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Located on a dome near the Wawona Tunnel, this National Park Service webcam provides a view of Yosemite Valley with snow blanketing the higher peaks on Thursday Sept. 21, 2017.

Fall begins early Friday afternoon, but parts of the Sierra Nevada Mountains already have a wintry look.

Snow fell in pockets of the towering mountain range Thursday -- the last full day of summer. Forecasters said the September snow is early but not unheard of, and is being caused by a cool weather system moving south from Oregon.

September and October snowfall is usually quick to melt as temperatures remain warm. It's not until November when temperatures dip enough for a blanket snow to stick around, hopefully until late winter or early spring, when the snowpack runs off the mountains and into California's system of canals and reservoirs.

National Weather Service forecaster Hanna Chandler said several inches of snow are expected at elevations of at least 6,000 feet in the northern Sierra.